Update 1/29/2018: Updated information in the section about adding a wire to the OEM connector. Options are adding a OEM pin to the stock socket or replacing the socket with a Toyota socket that has three wires already included.

Application:
2001-2004 1st generation Tacomas. The pre-2001 years don't have the same turn signal socket. You could replace the sockets or use a different switchback bulb, but this write-up is specifically for 2001-2004 trucks.

Part #:
Update 8/8/2017. The 3rd gen switchbacks VLED sells went obsolete. The only 3157 CK bulb they sell now seems to be this one. V6_KIT_WA_3157CK http://www.vleds.com/v6-triton-wa-3157ck.html It is on pre-sale as I write this. $120!

Note that we need the "CK" style bulbs (AKA SWACK style) as our sockets are a bit different from the standard 3157 style socket.

OLD part #s for reference:
Original V-LED part # (note these are no longer sold) 3157_60_WA2_CK_5K
2nd gen VLED part # 3157_42_WA2_CK_5K (no longer sold). The 2nd generation had impressively bright white LEDs. The brightness of the amber LEDs was fine/OK.
3rd gen VLED part # 3157CK_42_HV_WA_5K (no longer sold). I am still running these. The LEDs are holding up fine, but I have had to pop one of them apart to repair a connection.

Necessary changes:
If you just plug in the V-LED switchback bulbs, you get LED amber turn signals. To light up the white LEDs for running lights, you need to run 12V down to your turn signals. For more information on where to find a 12V source and how to hook up to it, check out this write up https://www.tacomaworld.com/threads/how-to-install-switchback-leds.150483/ The 2001-2004 Tacomas used a dual filament socket (has room for three wires), but Toyota only put two wires in for a single filament. You will be adding a wire to the empty spot on the socket OR you can try adding a pin to the socket or replace the existing socket with a Toyota socket that came with three wires.

Known problems: The switchback bulbs look for the turn signal voltage to know when they should turn off the white LEDs and flash the yellow LEDs. It is common for the white LEDs to go off briefly when you hit the brakes or switch into reverse. What happens is the rear driver's side light housing has a so-so ground and a bit of voltage develops on the ground when the brake lights or reverse lights are first turned on. That voltage travels through the rear driver's side bulb filament and to the "hot" side of the left turn signal. The switchbacks see that voltage and think you turned on your turn signal for a split second (the white LEDs then turn off for a second). There are two ways to get around this.
1. Add a ground wire from the rear driver's side light housing to the frame. This provides a better ground and keeps the voltage spike low. This is what I did..... partly because I was trying to figure out what the heck was going on and this help me prove it was the voltage spike I was seeing on the ground.
2. Change your rear brake bulbs to LEDs (they not only draw a lot less current, but don't have the big surge current when they first turn on). TW user DKA confirmed that replacing the brake lights with LEDs took care of the "winking" problem when applying the brakes. Another possible option is replacing the rear turn signal bulbs with LED. They should keep the voltage spike from the brake bulbs from getting to the "hot" of the turn signals. This should also take care of the "winking" when the reverse lights come on. I don't believe this has been tested.
Anytime you change your turn signals to LED you will get the dreaded hyper blink because the relay circuit thinks your turn signal is burned out (because the LEDs draw so much less current than incandescent bulbs). I highly recommend changing your turn signal relay to one meant for LEDs..... easy and doesn't need hot energy wasting load resistors. Here is one place that sells the LED relays http://www.autolumination.com/equalizers.htm

Here is the V-LED switchback bulb. You can see the amber and white LEDs.

Reach up behind the valence and unscrew the socket from the turn signal housing. The socket and stock bulb hang from the wires. Unplug the bulb.

Use a screwdriver to pry up on the tab to slide the socket apart. Ignore the blue quick-splice piece on my turn signal wire. That is for something else.

Looking at the socket, you can see two of the three holes have contacts in them. One hole looks big because it does not have a contact. This is where the added wire will go.

Pull the rubber plug out of the unused hole. You may want to put a slice in this plug so it will form better around the wire you are about to add.

Update 1/29/2018
The wire bent to form a pin was a bit half-ass. Over the years, the connection to the white LEDs has become bad a few times. Sometimes because moisture gets in there and sometimes because the "spring" made from the bent wire isn't pushing as much as it used to. I then have to pull the wire out, cut it, restrip it, and reform. I finally got around to looking for a more permanent solution.
There were two options I was exploring:

Keep the stock socket, but use an OEM pin so the connection should be as good as the ground and turn signal connections (as long as you seal it up just as well). I searched a lot and came across two OEM pins that may work.
82998-12170
82998-12340 Both of those appear to come with a few inches of wire so you don't need a crimping tool. You would just attach your 12V source for the white LEDs to the wire on those pins. I have not verified either work. If you can confirm either one works, please post and I'll make a note that it was confirmed.

Replace the socket with a Toyota OEM socket that came with three wires. I went with this option. I looked on Ebay and eventually came across a listing "97-99 Toyota Front Turn Signal Wiring Connector Plug OEM". It looked to be the exact same connector on our Tacomas, but with all three positions filled and a few inches of wire on each position. I ordered them and they fit perfect. All I had to do was connect the turn signal, ground, and 12V for white LEDs to the three wires coming off the connector (I soldered and then used heat shrink tubing to cover). The Ebay page listed Toyota Avalon, Camry, and Corollas '97-'99 as using that connector.

Here are the two sockets from Ebay. Different colors, but both fit great. You can see they have all three pins stuffed unlike our connectors that only have two pins stuffed.

The same connectors. Checking they mate with the turn signal bulb holder on our trucks.

The above options are the best way to get a third wire so you can power the white LEDs on the switchbacks, but in a pinch you can use a wire to form a contact. See below.
I fed the new wire in (18AWG wire) through the socket (from the back) and then bent the wire to form a hoaky spring type contact. Pull the wire back through until your created spring contact is about as deep in the hole as the two stock ones. Don't forget to put that rubber plug back in. It will keep water out of the hole and help keep the wire in place.

The added wire (the green in the last picture) has to go to a 12V source. This could be the cigarette lighter circuit (so the running lights come on as soon as you start your truck) or you could wire it to the corner lights (would only come on if your parking lights or headlights are on). I have mine so they come on if the ignition is on. Put your socket back together and screw it back into the turn signal housing. Here is the V-LED bulb lit up white with the headlights on.

The white LEDs are more white/blue than my headlights. The LEDs would probably match HIDs well or a incandescent bulb like the Philips Crystal Vision bulbs. Like other LED turn signals, they will cause hyper blink without a "load resistor" or similar. I modified the flasher relay circuit ( http://www.customtacos.com/forum/showthread.php?p=1670194 ), but load resistors would be the easy fix.

i did this mod today and for some reason when ever i tap the brake either 1 or both or the white leds goes completely off has anyone ever ran into this problem ...(ohh and i spliced into the parking light wire the green 1)

i did this mod today and for some reason when ever i tap the brake either 1 or both or the white leds goes completely off has anyone ever ran into this problem ...(ohh and i spliced into the parking light wire the green 1)

Click to expand...

Do the white LEDs turn off for about a second and then back on? If so, then you are probably getting a voltage spike on the turn signal wire that makes the switchback bulbs think you turned on the blinker for a split second. I noticed this only on my driver's side bulb which helped me diagnose the problem. This looks like this is the rule instead of the exception for these bulbs on our trucks.

You can do one of two things. 1. Solder a wire to your right (driver's side) rear turn signal socket (the ground of it) and run that to a nearby bolt that goes into the frame. I used about two feet of 16AWG wire. 2. Switch either your rear turn signal bulbs or rear brake bulbs to LED (I have not confirmed this fix, but it should work).